12 August, 2026

Review of The Influence of Averroes on European Thought: The Disappearance of Latin Averroism from the History of Philosophy by Koert Debeuf (Bloomsbury, 2024).

Abu al-Walid Muhammad ibn Ahmad ibn Muhammad ibn Rushd was born at Cordoba in 1126. He died at Marrakesh in 1198. His was a distinguished family of Muslim jurists adhering to the Maliki school, named for the 8^th-century Medinan scholar Malik ibn Anas (d. 795) who emphasised the established practices of the people of Medina. They were, the Malikis thought, a living continuation of Muhammad’s example, and their customs were a fertile source of law alongside the Quran and the Sunna. Ibn Rushd concurred, and was employed as a judge in Seville and Cordoba. He was also a physician, and produced a vast body of work embracing both law and medicine, among such other subjects as mathematics and grammar. Ibn Rushd is nevertheless chiefly remembered for his works of philosophy.

But Ibn Rushd never took his place alongside Al-Farabi, Al-Biruni, or Ibn Sina (Avicenna) in the Muslim intellectual firmament. His name has recently been given to a number of educational institutions in the Muslim world, but this exaggerates his impact on his coreligionists. It was in Christian Europe that Ibn Rushd had enduring influence—influence that was well understood and acknowledged for centuries and then suddenly forgotten. Ibn Rushd, or Averroes as he was known in Latin, should be regarded as one of the most influential figures from the high Middle Ages down to early modernity, and yet he isn’t. Koert Debeuf’s book The Influence of Averroes on European Thought offers an explanation, first taking stock of that influence and then explaining its apparent erasure.

The book is divided into two parts. It begins with the transmission of Averroes’ Aristotelian commentaries into the Latin West, through translators such as Michael Scot (1175–1232), the rise of radical Aristotelianism and Latin Averroism at the University of Paris, key doctrines including the unicity of the intellect and the relation of philosophy to revelation, and the ecclesiastical condemnations of 1270 and 1277. Debeuf singles out the notorious Averroist theory of the ‘double truth’, one known to reason and another to religion, and he subjects it to both historiographical and philosophical analysis. Next comes an examination of what Debeuf calls ‘political Averroism’, namely the idea that religion may be false but nevertheless useful. Debeuf proves that it was Giles of Rome (1243–1316) who mistakenly attributed this idea to Ibn Rushd and condemned it in his treatise Errores philosophorum. Ironically, this spread the idea far and wide, and Debeuf traces it through such later thinkers as Marsilius of Padua, Dante, Machiavelli, Spinoza, and Rousseau. That is the first part of the book. The second part follows the transformation of a ‘universalistic’ model of philosophy to a ‘Eurocentric’ one from which Arabic and Islamic philosophy was increasingly side-lined or deleted altogether.

Thomas Aquinas seems to have invented the term ‘Averroist’, or was at least the first to write it, in his treatise De unitate intellectus contra Averroistas. Perhaps Thomas also invented Averroism. Some have argued accordingly that there was in fact no coherent Averroism at all, or at least none beyond the theory of the unicity of the intellect attacked with unusual venom by Thomas. Those whom Debeuf calls ‘minimalists’ hold that Ibn Rushd had hardly any influence on European thinking in the thirteenth century and beyond. So go the arguments of Fernand van Steenberghen and his students and followers such as J. J. Duin and Bernardo Carlos Bazán which Debeuf analyses. No one in the 13^th century, they claim, followed Ibn Rushd in all his views. Even the notorious Siger of Brabant evolved towards Thomism and was not truly an Averroist. And so it is claimed that genuine Latin Averroism only began later with John of Jandun in the 14^th century. Others in this camp (such as Richard Dales) prefer labels such as ‘heterodox Aristotelianism’, ‘radical Aristotelianism’, or ‘independent philosophers’ and resist any implication that these masters intended positions contrary to Christianity, as Aquinas claimed.

Those whom Debeuf calls the ‘maximalists’ hold precisely the opposite view. For them, Ibn Rushd had a very substantial role in the formation of European philosophy and, they say, the birth of secularism. They accept a broader, more flexible understanding of influence: thinkers could be Averroists through partial adoption, mutation, inspiration, or even through the critiques levelled against them. The main maximalist luminary was Ernest Renan. His Averroès et l’averroïsme (1852) portrays Ibn Rushd as a symbol of free-thinking rationalism against religious dogma. Later maximalists, such as Pierre Mandonnet, Martin Grabmann, Bruno Nardi, Étienne Gilson, Alain de Libera, Jean-Baptiste Brenet, R. A. Gauthier, and Catherine König-Pralong, emphasise multiple ‘Averroisms’ varying by time and place. They note that even its opponents were influenced by Averroism, and stress that the very intensity of the attacks proves the movement’s importance and danger to orthodoxy.

Debeuf’s maximalist case for the influence of Ibn Rushd risks transforming a vast portion of European thought into what might be called ‘unconscious’ Averroism. But it is convincing nevertheless. It makes sense of all the histrionic attacks on Ibn Rushd from Thomas Aquinas onwards, even that of Plutarch who notoriously called Ibn Rushd ‘that mad dog’ who ‘barks against his Lord Christ and against the catholic faith’.¹ And it accords with the later humanist view that the Aristotelian heyday of the European universities and the development of natural science had a single inspiration.

Averroes awakened the studies of the Latins and provided the occasion to investigate nature in a serious manner for many who are now celebrated for this very reason. For the teaching of Averroes was so full of learning that he has found partisans who defend his opinions very fiercely even in our time, since they behold in them not only a straightforward narration of the peripatetic teaching, but they also find the knots of every problem undone. For he follows the Greeks and his own Arabs when they seem not to divert from the right path of philosophy, but when they are proven to have misunderstood, he upbraids them with many and indeed with stronger reasons (Avicenna, Liber Canonis in Medicina, Venice, 1556).

That is how Venetian physician Benedetto Rinio (1485–1565) reminds his readers of Ibn Rushd’s influence in his preface to a Latin edition of Ibn Sina’s Canon of Medicine, published in 1556. Ibn Rushd, accordingly, belongs to the western European trend towards the rediscovery of Aristotelian philosophy and the union of faith and reason which began in the 11^th and 12^th centuries with Anselm. He may have been a Muslim jurist, but he was not a foreign influence. Hindsight, like that of Benedetto Rinio, seems to prove this. And so obvious does it seem that it is easy to forget that the philosophy of Aristotle took hold despite considerable opposition and through a rather convoluted series of misunderstandings and overreactions. Debeuf gives a good precis and analysis of these developments, principally at the University of Paris. They culminated in the ‘condemnations’ of 1277 issued by Étienne Tempier, Bishop of Paris and former chancellor of the university there.

This brings us back to the question of Ibn Rushd’s influence. The central problem, it seems to me, is not the nature of that influence or how it faded away, but rather how it took shape in the first place. How did a Maliki jurist in Almohad Spain become such a gigantic figure of European thought? The answer is not straightforward. But Debeuf’s arguments would have benefitted from attempting to tackle it, beginning in the previous intellectual generation with Al-Ghazali (d. 1111). For he was the Iranian polymath and mystical theologian whose influence Ibn Rushd especially deplored and to which he reacted.

Al-Ghazali’s notorious turn against philosophy is habitually misunderstood by the likes of Neil DeGrasse Tyson, Ayaan Hirsi Ali, and their ilk. The treatise, known in English as The Deliverance from Error, is preoccupied with the kind of spiritual introspection made famous by Augustine, Rousseau, and Kierkegaard.² Al-Ghazali seems furthermore to anticipate both Descartes and the Postmodernists with his emphasis on doubt in the power of human reason and sensible knowledge.³ There is also an almost uncanny symmetry between Al-Ghazali and his near contemporary Anselm of Aosta: two highly learned men, maturing respectively at the eastern Iranian city of Tus overshadowed by a ruined Sasanian castle and at Aosta with its crumbling Roman amphitheatre and triumphal arch. Both men struggled with the relationship between faith and knowledge, but came to opposite conclusions. For Anselm, the propositions of Christianity were certain, necessary, and rational; for Al-Ghazali, faith was the only certainty.

Al-Ghazali believed that he could trust neither his intellect nor his senses — even regarding the existence of God and the truth of religion. Accordingly, he embarked upon a Descartes-like quest for absolutely certain knowledge ‘in which the object is revealed without any doubt at all’.⁴ For a long time Al-Ghazali was disillusioned, and afflicted as though by an illness until he realised that no discourse or argument would rescue him, but only divine grace. His intellectual health recovered, as he says, through the infusion of God’s light into his heart; and this he calls the only way to certainty. The reasoning of philosophers and theologians did nothing but worsen the spiritual and intellectual malaise which had surely afflicted many devout Muslims amidst the decline of the Abbasid Caliphate. Hence Al-Ghazali’s infamous treatise Tahafut al-Falasifa. The title is now commonly but not strictly accurately rendered as The Incoherence of the Philosophers. Its mediaeval Latin title gives a better sense of the book’s force: Destructio Philosophorum — The Destruction of the Philosophers. There, Al-Ghazali drives apart the synthesis of faith and reason which had so preoccupied Christendom since the time of Boethius, and the Muslim world since that of Al-Kindi. Philosophy, especially its Aristotelian variety, led only to various kinds of heresy or outright unbelief.

That was the general malaise to which Ibn Rushd reacted. And he aimed all his intellectual weapons squarely at Tahafut al-Falasifa. He tried to come to philosophy’s rescue with a vehement defence of both faith and reason in his famous book Tahāfut al-Tahāfut (commonly translated as The Incoherence of the Incoherence). His Faṣl al-Maqāl (usually called The Decisive Treatise) furthermore argues that philosophical reasoning is not only compatible with, but also required by, Islamic law. Both books amount to a thorough refutation of al-Ghazali’s claims in favour of faith alone.

Debeuf compresses this backdrop into only a few short paragraphs. The result is that Ibn Rushd’s later influence seems less surprising than it should. Al-Ghazali had the last word, and Ibn Rushd’s last-ditch effort to rescue philosophy did not achieve its desired end in the Muslim world. Two explanations for Ibn Rushd’s lingering influence over Christendom suggest themselves, however. The first is simply that he lived in the West, in what is now Spain and Morocco, far from Cairo, Damascus, and Baghdad. His work attracted the natural curiosity of neighbouring Jewish and Christian intellectuals and his fame spread from there. Second, Ibn Rushd’s numerous Arabic commentaries on Aristotelian texts were by far the best such works yet attempted in the West since Boethius had tried and failed to bring the Aristotelian texts into Latin. Ibn Rushd’s goal was to return to the ‘real’ Aristotle, purging contemporary understanding of Neoplatonic and other accretions. This was old hat in the Muslim world but new and exciting for Christian intellectuals.⁵ Outside Europe, the project was, in fact, hopelessly out of date, belonging properly to the bygone age of the Abbasid translation movement of the 9^th and 10^th centuries. Aristotle and Plato were new and exciting then, and determining the precise meaning of the Aristotelian texts seemed vital. But philosophy and conventional religion both declined, and Sufi mysticism, which Al-Ghazali especially favoured, was to triumph upon their ruins.

Ibn Rushd’s clarification of Aristotle was his most important work. These took various forms, conventionally known as the Short, Medium, and Long Commentaries, though some are more properly regarded as paraphrases. Herein lies another curiosity. Tradition holds that the impetus for such an intellectual effort was the Almohad caliph himself, Abu Yaʿqub Yusuf (r. 1163–1184), who had an interest in Aristotle, found his works obscure, and commissioned commentaries from Ibn Rushd. Caliphal interest is not entirely unbelievable, but what Ibn Rushd produced went far beyond the needs of a mere enthusiast. His were the vast, exhaustive works that the likes of Albert the Great, Thomas Aquinas, and company, had before them in Latin translation when weaving Aristotle into their Sentences and Summas.

Debeuf, understandably, passes over these details. But closer analysis might have led to some different conclusions. A more convincing explanation for the erasure of Ibn Rushd could be that he simply met the same fate as all other Western scholastic philosophers. Later scholars of the Renaissance and Enlightenment would come to come to look upon those gigantic scholastic tomes like the Sentences of Peter Lombard or Aquinas’ unfinished Summa Theologiae with their heavy, crabbed letters and abbreviations, thick columns of text, and cumbrous marginal notes and glosses — and nothing was more repugnant to them.⁶ They found no wit, humour, or style amidst all the intricate questions, responses, and mountains of syllogisms. The figure who was held to have inspired it all would surely be brushed aside also.

Among other texts, Debeuf takes as proof Bertrand Russell’s History of Western Philosophy. It fairly symbolises 20^th– and 21^st-century attitudes to Ibn Rushd’s place in the philosophical firmament, along with all the other ‘Arabians’. ‘Arabic philosophy’, says Russell, ‘is not important as original thought. Men like Avicenna and Averroes are essentially commentators’ (p. 426). That is how Russell dismisses Ibn Rushd, but he condemns Aquinas with even greater force:

There is little of the true philosophic spirit in Aquinas. He does not, like the Platonic Socrates, set out to follow wherever the argument may lead. He is not engaged in an inquiry, the result of which it is impossible to know in advance. Before he begins to philosophize, he already knows the truth; it is declared in the Catholic faith. If he can find apparently rational arguments for some parts of the faith, so much the better; if he cannot, he need only fall back on revelation. The finding of arguments for a conclusion given in advance is not philosophy, but special pleading. I cannot, therefore, feel that he deserves to be put on a level with the best philosophers either of Greece or of modern times (p. 462–463).

Instead of a creeping Eurocentrism that arbitrarily excluded Perso-Arabic, Egyptian, Babylonian, and other philosophies, we may be dealing with a very different phenomenon: a movement whereby, beginning in early modernity, intellectual inquiry in its paradigmatic form came to be restricted to the purely rational search for universal principles, eventually leaving, as in Russell, no place for faith. Ironically, Averroism provided the justification for this way of thinking.

Ibn Rushd was not an Averroist. But the Latin translations were fruitfully misunderstood, most especially so in the doctrine of the ‘double truth’—a misinterpretation of the theory of non-contradiction and complementarity between faith and reason. This doctrine was doubtfully associated with Siger of Brabant (c. 1240–1284) and Boethius of Dacia (fl. late 1260s–1270s), two masters at the University of Paris. But French scholar John of Jandun (1285–1328) is a better example.⁷ He always brackets together ‘Aristotle and the Commentator’, and follows them right up to the point of conflict with Christian orthodoxy. And there he halts to affirm what must be believed but cannot be proven. Here is an example from one of his discussions on the immortality of the soul:

Although the soul is within matter, its activity has nevertheless no share of physical matter. … According to our faith … the soul itself can suffer through a physical fire and be reunited with the body after death by command of God the Creator. However, I do not intend to bring forward any proof of those claims. But I consider that they should be believed by simple faith, as should many other things, without demonstrative reason, solely on the authority of holy scripture and approved by divine miracles … for the Doctors say that faith has no value where human reason provides proof.⁸

But that was not actually John of Jandun’s typical approach. Most of the time, when he reached an impasse, he cracks a joke.⁹ ‘I cannot prove it by any rational demonstration because I do not know that it is possible; if anyone does know, good for him’. ‘I do not know how to prove it; good for those who can!’. ‘I say that God can do it, but I do not know how; God knows’. And when it came to the conflict between creation of the world and the eternity of the universe, John urges us to believe in creation, even though it is philosophically impossible. No one who followed his reason and experience could ever infer that God made the world. ‘Besides’, John said, ‘creation is rare and happened only once, and that was a very long time ago’.¹⁰

And so, in the space of about two and a half centuries, European thought had gone from Anselm’s ‘I must believe in order to understand’ and Abelard’s ‘I must understand what I believe’ to ‘I cannot understand it but will believe it anyway’. It would only be a short leap from such an outlook to abandoning matters of faith altogether. The political Averroist idea ‘no religion is true, though it may be useful’, accused and spread by Giles of Rome, is a similar misunderstanding which leads in the same direction.

But the Averroist theory of the unicity of the intellect may not be a misunderstanding. It is found in Ibn Rushd’s commentaries on Aristotle’s De Anima. That text is notoriously dense and ambiguous at times. But, as Ernest Renan pointed out, a straightforward reading of Book III of that text seems to suggest exactly what the Averroists were accused of believing.¹¹ This is the twofold idea that the intellect has no bodily organ and therefore that intellectual activity is immaterial. Since it is impossible for immaterial things to be distinguished from one another without physical forms, Ibn Rushd concludes that there can only be one intellect. Mutual understanding of one matter or thing by several people is therefore really a single, universal phenomenon. Whether that seems reasonable or not, the idea is repugnant to orthodox Christianity for which the immaterial and immortal part of a man’s soul is personal and individual. The Averroist unitary soul implies that immortality is not personal, but collective. A brief progression of thought convinced Averroists that ultimate human felicity was only in the here and now.

Put these ideas together—double truth, non-religious political Averroism, and the unicity of the intellect—and you have the philosophical foundation for late mediaeval and early modern political theory, such as we find in Marsilius and Dante. The product is an intellectual armature for the separation of ecclesiastical and civil authority, official indifference to religion as long as it produces virtuous citizens, and an egalitarian, democratic vision of intellectual life. And so, perhaps Averroism was not ‘written out’ of European intellectual history so much as domesticated. In such a telling, Averroist tenets became obvious and self-evident before being taken for granted and forgotten.

Michael Bonner is a political consultant with a DPhil in Oriental Studies from the University of Oxford. His most recent book is The Crisis of Liberalism: the Origin and Destiny of Freedom (2026).

1. Petrarch, Rerum Senilium Libri, XV.vi. For analysis, see R. Irwin, ‘Petrarch and ‘that mad dog Averroës’ in G. MacLean (ed.), Re-orienting the Renaissance: cultural exchanges with the East, Palgrave Macmillan, New York, 2005, p. 108–125. ↩︎
2. Al-Ghazali, Deliverance from Error and The Beginning of Guidance, translated by M. Montgomery Watt, Islamic Book Trust, Kuala Lumpur, 2005 [originally published 1953]. ↩︎
3. M. Fakhry, A History of Islamic Philosophy, 3^rd edition, Columbia University Press, New York, 2004, p. 224–225. ↩︎
4. Al-Mundidh min al-dalal w’al-Mawsilu ila dhi al-‘izzati w’al-jalal, Maktabat al-Haqiqa, Ihya Press, 2016, p. 3. My translation. ↩︎
5. P. Adamson, Philosophy in the Islamic World: A History of Philosophy Without Any Gaps, vol. 3, Oxford University Press, Oxford, 2016, p. 179–186. ↩︎
6. R. W. Southern,  Medieval Humanism and Other Studies, Basil Blackwell, Oxford, 1970, p. 60. ↩︎
7. E. Gilson, Reason and Revelation in the Middle Ages, revised edition, edited by James K. Farge, with an introduction by William J. Courtenay, Pontifical Institute for Mediaeval Studies, Toronto, 2020 [originally published 1938], p. 43–45. ↩︎
8. This is from John of Jandun’s De Anima, III. qu. V, quoted in E. Gilson, Études de la philosophie médiévale, Commission des publications, Faculté des lettres, Palais de l’université, Strasbourg, 1921, p. 70–71. ↩︎
9. I am paraphrasing a selection of texts found in Gilson, Études de la philosophie médiévale, p. 72–75. ↩︎
10. John of Jandun, Physica, I. qu. 22, ad quaestionem in Gilson, Études de la philosophie médiévale, p. 75. ↩︎
11. E. Renan, Averroès et l’averroïsme: essai historique, August Durand, Paris, 1852, p. 122–128. ↩︎